The present invention concerns the field of methods of broadcasting television programs and the devices used in such methods. In particular, the invention proposes a broadcasting method for personalizing program streams for broadcast zones covered by a transmission network on a single modulation frequency in accordance with the DVB-T2 (Digital Video Broadcast—Terrestrial version 2) standard, the second version of the terrestrial video broadcast standard, or any related standard.
The networks for broadcasting digital services on a single modulation frequency or SFN networks (Single Frequency Networks) can be generalised in a certain number of broadcasting systems. There are for example the DVB-T (Digital Video Broadcasting—Terrestrial) broadcasting standards: “ETSI EN 300 744 V1.5.1, Digital Video Broadcasting (DVB); DVB-H (Digital Video Broadcasting—Handheld): “ETSI EN 302 304, DVB-H—Transmission System for Handheld Terminals”; or the Chinese standard DTMB (Digital Terrestrial Multimedia Broadcast) formerly called DMB-T/H (Digital Multimedia Broadcast—Terrestrial/Handheld) which use such SFN broadcasting networks.
The DVB organization has now standardized a second version for broadcasting television programs on a terrestrial network, under the name DVB-T2 ETSI EN302 755 V 1.2.1, and the invention fits in the context of this standard.
SFN networks are characterised in that the broadcasting of the services is effected by transmitting the same data stream by different transmitters on a single modulation frequency. Because of this, it is necessary for these different transmitters to receive exactly the same content and are finely synchronized together in order to avoid generating interference in the places situated at the junction of the coverage zones of the different transmitters.
This synchronization between the different SFN transmitters may, for example, be achieved by inserting, in the stream distributed to these transmitters, synchronization packets such as T2-MI (T2-Modulator Interface MIP), and MIP (Mega-frame Initialization Packet) packets of the DVB-T2 timestamp type, which correspond in the DVB-T2 standard to the timestamps used in the DVB-H and DVB-T standards. This mechanism is described in the document: “Digital Video Broadcasting (DVB); DVB mega-frame for single frequency network (SFN) synchronization modulator interface (T2-MI) for a second generation digital terrestrial television broadcasting system (DVB-T2)” of the ETSI (European Telecommunications Standards Institute) under the reference ETSI TS 102 773 V1.1.1 (2009-09). The transmission point receiving the stream is then synchronized on the stream received, for example by means of these T2-MI packets of the DVB-T2 timestamp type. This synchronization of the transmission point on the stream received, giving rise to the synchronization together of all the transmission points, is called the SFN synchronization of the transmission point.
SFN broadcasting is characterised by the definition of SFN areas. An SFN area is a geographical zone covered by a set of transmitters, the number of which is greater than or equal to one. These transmitters are finely synchronized and transmit exactly the same data stream on the same frequency.
The broadcasting of a set of programs in a data stream over a geographical zone is typically organized from a central point. The geographical zone covered is typically composed of a plurality of SFN areas. The plurality of programs broadcast comprises programs intended for all the zone covered and programs specific to a given region. The region being defined here as a set, possibly a single one, of SFN areas within the zone covered by the broadcasting and within which the programs broadcast are the same. National programs are usually spoken of in respect of programs broadcast over the whole of the zone and regional programs for programs broadcasted only over one or more regions.
The most simple solution for broadcasting these programs is to create one stream per region. This stream is composed, for each region, of all the national programs and the regional programs specific to this region. These various streams are then broadcast from the central transmission point and broadcast to the regions concerned. This solution poses a first problem, which relates to the duplication of the broadcasting of the national programs. This is because the typical broadcasting means is the satellite, the solution described multiplies the broadcasting of the national programs by the number of regions whereas ideally a single broadcasting of these programs could suffice. However, satellite bandwidth is expensive. A second problem relates to the fact that regional programs are typically available at the regions. The creation of the various streams therefore requires uploading these regional streams to the central transmission point in order to constitute the various streams necessary.